Download the demo version for free to test all the features. The demo version is limited to 3 emails, allowing you to figure out if EmailMerge.cc is the tool for you before buying one of the other full versions.
If you're happy with EmailMerge.cc's functionalities, you can:
The price is lifetime. No yearly license or any of that, you pay once and can use it as long as you want, all future updates and new features included (you won't need to buy new versions). If you buy the Enterprise version, you can also use that with an unlimited number of users.
There are three flavors of the Full Version:
Other than the number of users, all versions have the same features (multiple recipients in To, CC and BCC, adding attachments, High/Low priority, etc.)